1. Field of the Invention
The present invention relates generally to a position measurement device for measuring the position of a pen and a method for controlling the same, and more particularly, to a position measurement device and a control method thereof, by which some loops are used as transmitting/receiving loops and other loops are used as receiving loops.
2. Description of the Related Art
Recently, due to the rapid growth of the market related to smart phones and touch screens, related research is in progress. In order to input instructions in relation to a smart phone or a touch screen, a user may put a body part or an Electromagnetic Induction (EI) pen onto a certain position of a display to thereby input an instruction or select an icon.
The contact of a user's body part may be implemented by a capacitive type touch screen. The touch screen of a capacitive type generally includes a condenser between a transparent electrode and a transparent electrode. When a user's body part comes into contact with a touch screen, the touch of the user's body part is sensed, based on the change in capacitance of the condenser.
In this case, it is difficult to make a precise input in the capacitive type touch screen, because the contact of the user's body part onto the touch screen requires a relatively wide contact area. In contrast, an EI type touch screen has an advantage in that the operation can be made in a small contact area.
In the EI type touch screen, a loop coil, which is disposed in a circuit board, is applied with a voltage to thereby generate an electromagnetic field, and the electromagnetic field is controlled to be transferred to an EI pen. In this case, the EI pen includes a condenser and a loop and emits an electromagnetic field having a predetermined frequency in response to the transferred electromagnetic field.
The electromagnetic field emitted by the EI pen is transferred to the loop coil of the circuit board, so the position of where the EI pen approaches the touch screen can be determined.
In the typical EI type touch screen, all loop coils of the circuit board are supplied with an electrical current for electromagnetic induction in order to apply the electromagnetic field to the EI pen. The supply of an electrical current to the entire loop coils results in an increase in power consumption. Particularly, power consumption in the case of portable batteries of mobile devices may severely inconvenience the user.
In addition, since high voltage capability devices for applying an electric current having a great intensity to all of the loop coils are necessary, there are problems of an increase in the mounting area and high cost.